Tuesday, October 25, 2011

The amount of cesium-137 is more than twice the official number, and the amount of xenon-133 55% more, according to a new study using a larger data set, says Nature.

The study claims the amount of cesium-137 from Fukushima is half of that from Chernobyl, and the amount of xenon-133 from Fukushima far exceeds Chernobyl.

As the reason why the Japanese government numbers were low: the Japanese government probably only accounted for the radioactive fallout within Japan. So the large amount that went over the Pacific Ocean, reaching North America and Europe was never considered by the Japanese government.

The new study also claims that the Reactor 4 Spent Fuel Pool emitted a large amount of cesium-137.

The disaster at the Fukushima Daiichi nuclear plant in March released far more radiation than the Japanese government has claimed. So concludes a study that combines radioactivity data from across the globe to estimate the scale and fate of emissions from the shattered plant.

The study also suggests that, contrary to government claims, pools used to store spent nuclear fuel played a significant part in the release of the long-lived environmental contaminant caesium-137, which could have been prevented by prompt action. The analysis has been posted online for open peer review by the journal Atmospheric Chemistry and Physics.

Andreas Stohl, an atmospheric scientist with the Norwegian Institute for Air Research in Kjeller, who led the research, believes that the analysis is the most comprehensive effort yet to understand how much radiation was released from Fukushima Daiichi. "It's a very valuable contribution," says Lars-Erik De Geer, an atmospheric modeller with the Swedish Defense Research Agency in Stockholm, who was not involved with the study.

The reconstruction relies on data from dozens of radiation monitoring stations in Japan and around the world. Many are part of a global network to watch for tests of nuclear weapons that is run by the Comprehensive Nuclear-Test-Ban Treaty Organization in Vienna. The scientists added data from independent stations in Canada, Japan and Europe, and then combined those with large European and American caches of global meteorological data.

...The latest report from the Japanese government, published in June, says that the plant released 1.5 × 10^16 bequerels of caesium-137, an isotope with a 30-year half-life that is responsible for most of the long-term contamination from the plant. A far larger amount of xenon-133, 1.1 × 10^19 Bq, was released, according to official government estimates.

The new study challenges those numbers. On the basis of its reconstructions, the team claims that the accident released around 1.7 × 10^19 Bq of xenon-133, greater than the estimated total radioactive release of 1.4 × 10^19 Bq from Chernobyl. The fact that three reactors exploded in the Fukushima accident accounts for the huge xenon tally, says De Geer.

Xenon-133 does not pose serious health risks because it is not absorbed by the body or the environment. Caesium-137 fallout, however, is a much greater concern because it will linger in the environment for decades. The new model shows that Fukushima released 3.5 × 10^16 Bq caesium-137, roughly twice the official government figure, and half the release from Chernobyl. The higher number is obviously worrying, says De Geer, although ongoing ground surveys are the only way to truly establish the public-health risk.

Stohl believes that the discrepancy between the team's results and those of the Japanese government can be partly explained by the larger data set used. Japanese estimates rely primarily on data from monitoring posts inside Japan, which never recorded the large quantities of radioactivity that blew out over the Pacific Ocean, and eventually reached North America and Europe. "Taking account of the radiation that has drifted out to the Pacific is essential for getting a real picture of the size and character of the accident," says Tomoya Yamauchi, a radiation physicist at Kobe University who has been measuring radioisotope contamination in soil around Fukushima.

Stohl adds that he is sympathetic to the Japanese teams responsible for the official estimate. "They wanted to get something out quickly," he says. The differences between the two studies may seem large, notes Yukio Hayakawa, a volcanologist at Gunma University who has also modelled the accident, but uncertainties in the models mean that the estimates are actually quite similar.

The new analysis also claims that the spent fuel being stored in the unit 4 pool emitted copious quantities of caesium-137. Japanese officials have maintained that virtually no radioactivity leaked from the pool. Yet Stohl's model clearly shows that dousing the pool with water caused the plant's caesium-137 emissions to drop markedly (see 'Radiation crisis'). The finding implies that much of the fallout could have been prevented by flooding the pool earlier.

9
comments:

kintaman
said...

So can we please arrest those responsible for this NOW and have them face firing squads or whatever other harsh punishment they deserve. Better yet, send them to work in the nuclear reactors first hand.

Those responsible:

- TEPCO CEO who recently retired to escape.- TEPCO top executives and upper management.- Japanese government top officials.- So called "experts" who misinformed so many people about the dangers.- Media top officials and even announcers who lied.- Whoever made the order which prevented the TEPCO people on site from using Sea Water right away when they knew what had transpired. This is what contributed in a large way to the disastrous releases of radionuclide materials.

Do NOT let these criminals get away. Put these people on site at Fukushima Daiichi. Why should they be allowed to escape the results of their decisions and crimes?

"Stohl adds that he is sympathetic to the Japanese teams responsible for the official estimate. "They wanted to get something out quickly," he says.

The "something out" they wanted to get was their stipend promised from TEPCO.Seriously, how could any self-respecting scientist NOT calculate effects from wind transport to sea, their ace in the hole.

9:03, more detailed analyses will tell you that it would not have mattered if they did attempt to use ocean water right away. Once core melting occurs the problem transforms into something designed almost to hinder any attempt at radiation releases.

This explains the amount of cesium being discovered. Read following from site, Story Behind the Story, Dr. A.T. Ott.

There are about seven isotopes of xenon that are radioactive and would be released in such an incident, with atomic masses of 133, 135, 137, and 138, along with three isomers, 131m, 133m, and 135m. With the exception of the isomers, each of these xenon atoms will decay into cesium and some into other elements past cesium. There is also krypton but its radioactivity and decay products are of less concern. Xenon itself is not particularly dangerous. It is a noble gas and is not concentrated in the body. Cesium is more of a concern. Here are the seven decay sequences: Xenon-131m will decay to stable xenon-131.Xenon-133m will decay to radioactive xenon-133.Xenon-133 will decay to stable cesium-133.Xenon-135m will decay to radioactive xenon-135.Xenon-135 will decay to very mildly radioactive cesium-135.Xenon-137 will decay to radioactive cesium-137.Xenon-138 will decay to radioactive cesium-138 and then quickly to stable barium-138. Of all of these, the decay of xenon-137 to cesium-137 is probably responsible for the most risk, but xenon-137 decays so quickly that the mobility of cesium-137 is limited. I do not think this poses much risk because it can’t get far. "

Fukushima still continues to emitt radionuclide fallouts. Let's please be careful not to speak or write about Fukushima as if the releases were over.They are not, the crisis is not over, the emissions are still ongoing, via air, vapors or water. Sentences such as "...Reactor 4 Spent Fuel Pool emitted..." or "...The disaster at the Fukushima Daiichi nuclear plant in March released..." make it seems like the emissions are over.

Exactly as Anonymous 4:15 says, this is far from over. Many report it as though it is done and over with. Even my friends, family and coworkers back in Japan talk as though it is over. It is not as the fuel from the reactor cores are open to the air in the ground and also the spent fuel rods are in an unconfirmed state. Also, so much fuel has been spread around and now there are reports of reactors 5 and 6 being in danger.

The report said 78% of the cesium went into the ocean. I'm not comforted by that. This means more cesium in fish, algae, and entering the global ocean currents which can then push ashore onto sandy beaches all over the world.

The ocean is also involved in the rain cycle, so that could mean more radioactive rain.

Interesting paper. I think their most important point, as summarized by the article above, is as follows:

"The new analysis also claims that the spent fuel being stored in the unit 4 pool emitted copious quantities of caesium-137. Japanese officials have maintained that virtually no radioactivity leaked from the pool. Yet Stohl's model clearly shows that dousing the pool with water caused the plant's caesium-137 emissions to drop markedly (see 'Radiation crisis'). The finding implies that much of the fallout could have been prevented by flooding the pool earlier."

However, if you read the paper, you'll see that the authors spent remarkably little effort on the causality here. They seemed satisfied that because A and B happened at roughly the same time, A must have caused B. Meanwhile, those of us who remember those harrowing days saw how fluid and dynamic the situation was, but the authors devote zero ink to considering other possible factors.

In the end, I think they may very well be right, but they do themselves a disservice for not tackling this issue more thoroughly.

(In any event, this is why papers are submitted for discussion prior to being published! I trust that they will rectify some of this prior to publication.)

About my coverage of Japan Earthquake of March 11

I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

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